Conventional radio video transmission systems transmitting video data by radio include those which transmit video data from AV (Audio & Visual) equipment using a very weak radio wave and those which are utilized for Wireless LAN (Local Area Network) and which use a spectrum spread communication.
A television signal transmission apparatus described in JP Utility Model Publication (Kokai) No. 3-482 U (1991) is a specific example of a system transmitting video data using a very weak radio wave according to the above conventional technique. A radio video signal transmission and reception apparatus described in JP Patent Publication (Kokai) No. 10-173571 A (1998) is a specific example of a system transmitting video data using a spectrum spread communication.
Both radio video transmission systems may not transmit video data easily if their radio environments are degraded by interference by another piece of radio equipment or a change in the distance between a transmitter and a receiver resulting from operation during movement.
If video data cannot be transmitted easily, transmission of video data may be enabled by for example, switching a frequency band used for radio transmission or changing a compression rate for video data to reduce the amount of data transmitted.
Specifically, the receiver of the radio video transmission system receives video data to recognize the degradation of the radio environment. The receiver then transmits an instruction on the switching of the radio frequency band or the change in the compression rate for the video data, to the transmitter. Upon reception of the instruction, the transmitter executes a process in accordance with the instruction.
To achieve this, the user of the receiver recognizes the degradation of the radio environment while viewing and listening to the received video data. The user thus transmits the instruction on the switching of the radio frequency band or the compression rate for the video data, to the transmitter by radio.
Examples of documents relating to the above technique are listed below.    1) JP Utility Model Publication (Kokai) No. 3-482 U (1991)    2) JP Patent Publication (Kokai) No. 10-173571 A (1998)
However, these systems cannot enable the transmission if the radio environment is degraded to the degree that the receiver cannot transmit the instruction on the switching of the radio frequency band or the video data compression rate, to the transmitter. In this case, the user having recognized the degradation of the radio environment must directly visit the location of the transmitter and perform an operation for switching the radio frequency band or the video data compression rate. Accordingly, this user interface is disadvantageous.
The present invention is made in view of the above problems. It is an object of the present invention to provide a system and method for radio video transmission which allows the radio frequency band or the video data compression rate to be switched to enable appropriate video transmissions even if the radio environment is significantly degraded.